Optimization of rechargeable zinc-air battery with Co3O4/MnO2/CNT bifunctional catalyst: effects of catalyst loading, binder content, and spraying area

Abstract

The air cathode is the most crucial component for a zinc-air battery (ZAB) system, which inquires fast diffusion of gaseous O2 and decent bifunctional catalytic performance. Herein, based on our previous attempts, we developed a bi-functional electro-catalyst utilizing co-doped manganese dioxide nanotube/carbon nanotube (CNT) composite to improve the catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A simple characterization of the morphology and physicochemical properties of various Co3O4/MnO2/CNT (CMC) composites was performed by employing various techniques (SEM, TEM, and XRD). More importantly, using CMC composite as the bifunctional cathode catalysts, we thoroughly investigated the effects of catalyst loading, bonding layer loading, and spraying area in catalyst layer (CL) on cell performance and charge-discharge cyclic ability for rechargeable zinc-air batteries. The highest peak power density of 400.3 mW cm−2 can be reached when the catalyst loading is 3 mg cm−2, the spraying area is 1 cm2 and the binder content is 80 μL. The rechargeable zinc-air batteries with the air electrodes containing different spraying areas and bonding layer loadings are stably operated for 22 h at a high current density (100 mA cm−2) and show a maximum voltage gap of 1.5 V between charge and discharge voltages. All these optimization efforts are particularly important to future large-scale applications in ZAB.